The recent discovery of earthlike planet Kepler 186f has attracted the attention of exobiologists who might have otherwise been distracted by recent discussion of possible extraterrestrial life on Jupiter's moon Europa, Saturn's moons Enceladus and Titan, or (long shot though it may be) Mars.
In four years with the launch of the James Webb Space Telescope (JWST), we may be able to find out whether planets like Kepler 186f have surface-level, oxygen-producing plant life. But existing telescope and probe technology has already pretty much eliminated the possibility of anything so pedestrian in our own solar system. If there's life nearby, it's going to be extreme.
NASA exobiologist Richard B. Hoover specializes in the study of extremophiles, and his work has shown the degree to which life on Earth can thrive in what we would consider to be harsh environments:
What we're generally looking for when we look for our life in our own solar system is something that can survive under the surface (because we've seen the surface of every warm terrestrial planet or moon), something that can survive in very low temperatures, and something that does not need to breathe an earthlike atmosphere.
Does this preclude the possibility of intelligent extraterrestrial life in our solar system? I think it precludes the possibility of intelligent terrestrial life, but there is a real—albeit slim—possibility that something as intelligent as a dolphin (i.e., pretty darn intelligent) could be swimming underneath the waters of Europa or Enceladus. Until we've had a firsthand look, we just can't say for sure.